EnergyFree Energy and Spontaneous ReactionsCatalysts/EnzymesRedox ReactionsRedox ReactionsElectronegativityFour Metabolic Stages of Cellular RespirationOverview1. Glycolysis2. Bridge Reaction3. Krebs Cycle (The Citric Acid Cycle)4. Oxidative PhosphorylationPhotosynthesis OverviewChloroplastsChemical Reaction for PhotosynthesisPhotosynthesisLight ReactionThe Calvin CycleSunlightWavelike PropertiesParticle Like PropertiesLight ReactionStep by Step ProcessThe Calvin Cycle3-Step ProcessChapter 8: An Introduction to Metabolism- Metabolism—the sum total of an organism’s chemical reaction.- There are two types of metabolisms: Catabolic and Anabolico Catabolic—pathways involved in degradation. Release energy by breaking down complex molecules to simpler compounds.o Anabolic—pathways involved in synthesis. Consume energy to build complicated molecules from simpler ones. Sometimes called biosynthetic pathways.o Every chemical reaction in the body is either building something or breakingit down and falls in one of these categories.Energy- Organisms transform and transfer energy- Energy—the capacity to do work- Potential Energy—energy that an object possesses because of its structure or position. Usually chemical bond energy in biological systems. Potential energy is usually based on location or position. It often refers to energy that is in chemical bonds.o Example: a ball at the top of a hill has a lot of potential energy. The ball at thebottom of the hill does not.- Kinetic Energy—the relative motion of an object. Every time there is motion, energy is released. Kinetic energy can also be based upon position.- Energy transfers by organisms are subject to two laws of thermodynamicso First Law of Thermodynamics—energy can be transferred and transformed, but it cannot be destroyed (i.e., the energy of the universe is constant). The amount of energy in the universe is constant; we are not losing or making energy, it is being transformed. The first law of thermodynamics is known as the principle of conservation of energy. Example: according to this law, Einstein would be right to say that reincarnation exists because energy is not lost when we die.o Second Law of Thermodynamics—every energy transfer or transformation makes the universe more disordered (i.e., every process increases entropy). In other words, with every transfer of energy, some usable energy is lost as “heat”. There isn’t a completely perfect transfer of energy because some of the energy that could’ve been used to do work is lost as heat. For example, with working out, your energy is not only used for doing weights or cardio because some of it is lost as heat—this is why we get hot when working out. Entropy (S)—the quantitative measure of disorder or randomnessFree Energy and Spontaneous Reactions- Free energy (G)—the portion of energy available to do work ΔG = ΔH - TΔS- Free energy is the difference between the total energy (ΔH, or enthalpy) and the energy not available to do work (TΔS), where T is the absolute temperature and S is entropy.Chemical Reacti ons- In a chemical reaction, the energy change (ΔG) between the reactants and the products is the amount of useable energy that can be harvested to do work. ΔG = ΔH – TΔS, where ΔG = G Final Products – G Starting Material (reactants)o If you use this equation and ΔG is negative, it means that energy was released by the reaction.o If you use the equation and ΔG is positive, it means that the energy of the products was higher than the energy of the reactants.- As a chemical reaction approaches equilibrium, the free energy (ΔG) of the system decreases.- When a reaction is pushed away from equilibrium, the free energy (ΔG) of the system increases.- At equilibrium, ΔG=0. At equilibrium, no work can be done.ΔG- If ΔG is negative, the forward reaction will occur spontaneously, and energy will be released.- If ΔG is positive, the forward reaction will not occur spontaneously, energy will haveto be added to the system in order for the forward reaction to occur.Types of Chemical Reacti ons- Types of reactions are based on their free-energy changes.- Exergonic Reactions—release energy when they occuro Products have less free energy than the reactantso Reaction is energetically downhillo Spontaneous reactiono ΔG is negative- Endergonic Reactions—require input of energy to occuro Products have more free energy than reactantso Reaction is energetically uphillo Non-spontaneous reaction (requires an energy source)o ΔG is positive- Figure 8.6a—exergonic reactiono If you were to subtract the reactants from the products, you would get a negative number- Figure 8.6b—endergonic reactiono If you were to subtract the reactants from the products, you would get a positive number- Figure 8.9—hydrolysis of ATPo One of the most exergonic reactions in cells is the hydrolysis of ATP. When water is added to ATP, the negatively charged oxygen ions from the phosphate groups repel the water and an inorganic phosphate group is released. The release of the phosphate group releases a bunch of energy.o High energy molecule These phosphate bonds aren’t really “high-energy” as they are often referred to. The reason that ATP is a high-energy molecule is that the products (ADP + P) have substantially lower free energy than the reactants. This means that the energy difference between the products and reactant is enormous, which will provide a lot of energy to do work.o Phosphate tail The structure of the ATP molecule is what makes it such an efficient energy source. (Form dictates Function) The 3 phosphate groups all located next to each other have negative charges. Like charges repel. The phosphate tail is like a compressed spring. When one of these bonds is broken, a huge amount of energy is released- How does ATP drive work?o If the change in free energy ΔG for an endergonic reaction is less than the amount of energy released by ATP hydrolysis, then the 2 reactions can be coupled so that overall, the reactions are exergonic.o Coupled reactions—energy released from exergonic reactions (ATP hydrolysis) are used to power endergonic reactions.Catalysts/Enzymes- Catalysts are substances that speed up the rates of exergonic chemical reactions butare not themselves used up or altered.- Enzymes are biological catalysts. Most enzymes are proteins. Enzymes are highly specific for the chemicals they act on.- Activation
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